Pump.



- PATENTED OCT. 8. 1907.

8; G. SKINNBR.

PUMP.

APPLICATION FILED MAR. 30, 1905.

WITNESSES f @wyM STEPHEN GUION SKINNER, OF CHICAGO, ILLINOIS.

PUMP.

Specification of Letters Patent.

Patented Oct. 8, 1907 Application filed March 30,1905. Serial No-252,838.

To all whomit may concern:

Be it known that I, STEPHEN GUIoN SKINNER, a citizen of the UnitedStates, residing at Chicago, county of Cook, and'State of Illinois, haveinvented new and useful Improvements in Pumps, of which the following isa specification.

' My invention relates to improvements in air pumps with a specialreference to that class of pumps'shown and described in Letters Patentof the United States to Hubert J. Rock dated July 12, 1904. r

The object of this invention is to so arrange the interior parts thatthe work will be principally done on the down stroke, the pumps beingdesigned to be operated manually. It has been found that while greaterforce may be executed by lifting on the pump handles on a single stroke,there is an advantage in having the work done on the down stroke, as theweight of the person is thus utilized and the operator does not tire asquickly as would otherwise be the case. I

In the following description reference is had to the accompanyingdrawings, in which The figure is alongitudinal sectional view of a pumpembodying my invention.

1 is a base, preferably constructed in the form of a stirrup for thereception of the toe or foot of the operator, 2 is a stationary cylindermounted upon the base and 3 is a stationary inner cylinder also mountedon the base and arranged in communication with a duct 4, leading to aflexible tube 5, having a clamping thimble at 6, whereby the tube 5 maybe connected to the receptacle, to which air is to be supplied. Atubular piston rod 8 is arranged to extend downwardly between the tubes2 & 3 and is provided at its lower end with a cup leather piston 9,filling the space between the piston rod 8 and the outer cylinder 2. Thelower end of the piston rod 8 is also provided with an interior headpiece 1.1 having suitable packing around the inner stationary cylinder 3as shown through which a passage 12 extends, with a valve at 13 adaptedto permit air to pass to the interior of the piston rod 8. The upper endof the inner stationary cylinder 3 is provided with a piston 14preferably of the cup leather type and with the leather extendingupwardly along the inner face of the tubular piston rod, so as to permitair to pass freely upwardly to the upper end of the rod. The upper endof the cylinder 3 is also provided with a spring actuated check valve at15 which permits air to pass from the upper end of the rod 8 into thecentral tube 3, but prevents its return.

In operation, air is admitted to the outer cylinder 2 through anaperture at 16. On the upstroke of the piston rod 8, the air passes thecup leather piston 9 to the lower end of the cylinder 2 and on the downstroke, this air is forced upwardly through the passage 12 to theinterior of the piston rod 8. On the next up stroke, this air is drivenpast the cup leather piston 14, which also serves as a valve, and on thenext down stroke, the air is forced past the valve ,at 15 to the innercylinder 3.

The up stroke is not a compression stroke, the air being merelydelivered past the cup leather 14. All the work is therefore performedon the down stroke, the gain over a single piston pump being due to thefact that the high compression is performed in a cylinder of smalldiameter, While the low compression, which requires but little work, isperformed in a large cylinder and the relative length of stroke againstlow resistance is therefore greatly .reduced, while the force requiredis distributed owing to the fact that a high compression begins in thesmall cylinder at the beginning of the stroke and reaches the maximumwith the beginning of air delivery through the valve 15 after a shortinterval.

With the described construction, it will be observed that no packing isrequired for the tubular piston rod 8, air being permitted to freelyenter the outer cylinder above the cup leather piston 9, since the cupleather of this piston is turned downwardly. It will also be observedthat the cup leathers of the pistons 9 and 14 both bear outwardlyagainst the inner surfaces of the cylinder 2 and piston rod 8respectively. By thus avoiding inner ,bearing cup leathers, either forpacking or for the pistons, leakage is avoided, since an inward bearingcup leather tends to form wrinkles which permit the passage of air.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is,

In a pump of the described class, the combination of a base; inner andouter stationary cylinders rigidly c011- nected therewith; a tubularpiston rod extending downwardly between the upper ends of the cylinders;a piston on the lower end of said rod having a down-turned cup leatherworking on the inner surface of the outer cylinder; and a piston on theinner cylinder having an lip-turned cup leather working on the innersurface of the tubular piston rod, said piston rod being provided with avalved passage leading to the interior of the rod from below the firstmentioned piston, and said inner stationary cylinder being; providedwith a valved passage leading to the interior of the inner cylinder fromabove the other piston.

In testimony whereof I afiix my signature in the presence of twowitnesses.

STEPHEN GUION SKINNER.

Witnesses:

H. H. CANNON, G. W. MILLER.

